Process of manufacturing ammonium sulfate.



'GERHARD NICOLAAS VIS, F CUISE-LAMOTTE, FRANCE.

PROCESS, OF MANUFACTURING AMMONIUM SULFATE.

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, able others skilled in the art to which it appertains to make and usethe same.

This invention relates to the manufacture of ammonium sulfate and it hasfor its object to enable this compound to be obtained in a far moreeconomical mannerthan heretofore.

It consists in the hereinafter described 1mproved process of producingammonium sulfate by causing gypsum (hydrated sul-v fate of calcium) toreact with ammonium carbonate under conditions adapted to directlyproduce a concentrated lye of pure ammonium sulfate without evaporationof water.

It is well known, that ammonium sulfate can be obtained by convertingammonium carbonate with readily soluble sulfates such as alum, as wellas with sulfates which only dissolve with difliculty such as gypsum thatis to say hydrated calcium sulfate (Graham Otto, 5th ed., 3 div., pag.482). Both reactions have been proposed for obtaining ammonium sulfatefrom gas liquor, the stoichiometrical amount of alum being added to thegas liquor in the first method and the gas liquor being passedrepeatedly through a layer of gypsum in the second method. Neither ofthe two proposals. however attained technical importance and in practiceammonium sulfate 1s prepared now as before by the reac- -t1on of ammoniavapors on sulfurlc acid.

The directions given by Graham Otto at the above cited passage ofliterature for the use of gypsum, according to which the as liquor hasto be passed repeatedly throng a layer of gypsum, must on account of thedifficulty with which gypsum dissolves in water lead to the assumption,that the reaction between it and the ammonium carbonate requires besidesalong time a large amount of water, so that only dilute solu-Specification of Letters Patent.

Patented A 311, rare.

Application filed June 7, 1911. Serial No. 631,799.

tions can be obtained, because it must be ex pected that after theformation of a certain amount of ammonium sulfate, an equilibriumresults andthat this on account of the slight solubility of gypsum inwater, oc curs at a very low concentration of ammonium sulfatefAccording .to this the said process, whichcould not even obtain anyimportance for the treatment of gas liquor was bound to prove unsuitablefor the production of ammonium sulfate on a manufacturing scale, onaccount of the great cost of evaporation which. was evidently attachedto it. Furthermore this process is absolutely technically impossiblebecause on evaporation of the ammonium sulfate solu-' tion the freeammonia contained in large quantity in the gas liquor (and which as iswell known does not react with gypsum to form sulfate) is lost. Now Ihave discovered the very surprising fact that the conversion of gypsumwith ammonium cars bonate into ammonium sulfate can be quickly andsmoothly effected by using a concentrated solution of ammonium carbonateand that under this condition the reaction goes on even in a'saturatedsolution of ammonium sulfate with the efiect that finally ammoniumsulfate is precipitated. If for instance finely powdered gypsum andammonium carbonate are mixed together,

and if an amount of water is added, which is by far insuflicient todissolve the corresponding amount of ammonium sulfate, very soon areaction takes place, which continues as long as ammonium carbonate andcalcium sulfate are present in sufficient quan tities, whereby ammoniumsulfate is precipitated. The gypsum need not even be finely divided. Inaconcentrated solution consists in carrying out the well known reactionbetween ammonium carbonate and gypsum in concentrated solutions for thetion ammonium carbonate in any suitable form is dissolved in water. Theconcentrated solution is brought together and mixed with gypsum reducedto a fine powder. A thickening of the whole mass takes place and after ashort time calcium carbonate is precipitated, Whereas ammonium sulfateis found to be present in the liquid.

If the ammonium carbonate is employed in the form of an acid salt carbondioxid is briskly evolved and the solution contains ammonium sulfatemixed with a little calcium bicarbonate which as is well known can bereduced by boiling to calcium monocarbonate which separates out.

Another very advantageous way of carrying out the new process isthe'following:- Gaseous carbon dioxid for instance in the form offurnace gases (containing 10 to 15% carbon dioxid) and ammonia vaporsfor instance derived from the waste waters of gas, coke works, and thelike, are passed through a Watery suspension of gypsum. The reaction iscarried through in such manner that it corresponds to the followingHowever an excess of carbon dioxid may be employed, in order to avoidammonia being carried away by the escaping inert gases.

A third way-of carrying out the new process'consists in leading a waterysolution of ammonia as concentrated as possible such for instance as isobtained from the stills of gas works, into a thick watery suspension ofgypsum into which simultaneously carbon dioXid or furnace gases arepassed, care being taken, that the carbon dioxid is always present inexcess. The gypsum is kept in suspension by means of stirrers and ifnecessary calcium bicarbonate present in the so- 'lution obtained isdecomposed by boiling.

The whole mass is then filtered by means of a filtering press. Ifdesired the clear solution may be evaporated to obtain ammoniumsubjecting in said concentrated solution gypsum to the action ofammonium car bonate, and separating the ammonium sulfate producedthereby from the calcium carbonate.

2. The process of manufacturing ammonium sulfate consisting in producinga concentrated solution of ammonium sulfate of at least thirty per cent.concentration and subjecting in said concentrated solution gypsum to theaction of ammonium carbo nate and separating the ammonium sulfateproduced thereby from the calcium carbonate.

3. The process of manufacturing ammonium sulfate consisting in producinga concentrated solution of ammonium sulfate and subjecting in saidconcentrated solution gypsum to the action of ammonium carbonatestirring, the mass produced thereby and separating the ammonium sulfatefrom the calcium carbonate.

4. The process of manufacturing ammonium sulfate consisting in producinga concentrated solution of ammoniumsulfate of at least thirty per cent.concentration and subjecting in said concentrated solution gypsum to theaction of ammonium carbonate stirring the mass and se arating theammonium sulfate produced rom the calcium carbonate.

5. The process of manufacturing ammonium sulfate consisting inemulsifying gypsum in water and subjecting such emulsion to the actionof ammonium carbonate thereby forming a concentrated solution ofammonium sulfate and subjecting gypsum to the action of ammoniumcarbonate in said concentrated solution and separating the ammoniumsulfate produced thereby from the calcium sulfate.

6. The process of manufacturing ammonium sulfate consisting inemulsifying gypsum in water and subjecting such emulsion to the actionof ammonium carbonate thereby forming a concentrated solution ofammonium'sulfate of at least thirty per cent. concentration andsubjecting gypsum to the action of ammonium carbonate in saidconcentrated solution, and separating the ammonium sulfate producedthereby from the calcium sulfate.

7. The process of manufacturing ammonium sulfate consisting inemulsifying gypsum in water and subjecting such emulsion to the actionof ammonium carbonate thereby forming a concentrated solution ofammonium sulfate and subjecting gypsum to the action of ammoniumcarbonate insaid concentrated solution, stirring the mass and separatingthe ammonium sulfate produced thereby from the calcium sulfate.

8. The process of manufacturing ammo-- nium sulfate consisting inemulsifying gypsum in water and sub ecting such emulsion to the actionof ammonium carbonate thereby forming a concentrated solution of ammoniuifi'sulfate of at least thirty per cent. my hand in presence of twosubscribing wita concenfiation and subjecting gypsum to the nesses.

action of ammonium carbonate in said coni centrated solution, stirringthe mass and GERSHARD NICOLAAS V separating the ammonium sulfateproduced Witnesses: thereby from the calcium sulfate. MARGEL DENIs,

In testimony whereof I have hereunto set AUGUST OOSTERMAN.

